In a roped-elevator, a car connected with a counter weight by a rope travels up and down with a hoist machine winding the rope up and down. A conventional speed control apparatus for the roped-elevator to control the speed of the car is shown in FIG. 8. A speed convert circuit 14 inputs a car speed command value Vcref and converts the car speed command value Vcref to a motor speed reference value Vmref1, where the motor drives the hoist machine. The motor speed reference value Vmref1 is calculated by using constants including a diameter and a rotational angular velocity of a sheave of the hoist machine. A follow-up control circuit 15 inputs a deviation value Vce1 between the motor speed reference Vmref1 and a actual motor speed Vm from a motor speed detecting circuit 5 and calculates a motor speed correction signal Vce2 for the actual motor speed Vm following-up the motor speed reference value Vmref1. This follow-up control circuit 15 is provided with a P (proportional) factor which outputs a signal proportional to the deviation value Vce1 and an I (integral) factor which outputs a signal proportional to a cumulative value of the deviations Vce1.
A motor 16 is a type of an induction motor for driving the elevator. A power from the motor is transmitted to an elevator mechanical system 4 and a car speed Vc changes. Here, the elevator mechanical system 4 represents the whole mechanical system of the elevator including the rope, the car and the counter weight. A resolver is used as the motor speed detecting circuit 5 and it outputs pulses where the number of the pulses per unit time is proportional to its rotational speed.
A vibration suppress circuit 17 in-puts a deviation Vrip (vibration components) between the actual motor speed Vm from the motor speed detecting circuit 5 and a presumed motor speed Vmobs from a motor speed presuming circuit 18 and outputs a compensation component signal Vb against the vibration. FIG. 9 shows an inner schematic structure of the vibration suppress circuit 17. The vibration suppress circuit 17 is provided with a filter circuit 19 for eliminating a vibration component of the motor speed and a gain setting circuit 20 for multiplying the vibration component by a gain to output the vibration compensation signal Vb. The filter circuit 19 defines the most pertinent filter constant based on a car position detected signal y from a car position detecting circuit 10, and passes only a given frequency component in the deviation signal Vrip of the vibration between the actual motor speed Vm and the presumed motor speed Vmobs. The gain setting circuit 20 defines the most pertinent gain based on the car position detected signal y and a car load detected signal mc from a car load detecting circuit 9 and outputs the vibration compensation signal Vb calculated by multiplying an output from the filter circuit 19 by the gain. As set forth above, the vibration suppress circuit 17 calculates the vibration compensation signal Vb for suppressing the vibration caused by the changes of the car position and the car load and adds the signal Vb on a motor speed correction signal Vce2 outputted from the follow-up control circuit 15. As a result, the added signal (Vce2-Vb) is inputted as a motor speed reference value Vmref2 to the motor 16 and the motor 16 can rotate smoothly without vibrations.
Here, the car position detecting circuit 10 includes a pulse generator mounted on a governor and evaluates the car position from the number of the pulses generated proportionally to a distance of movement of the car. The car load detecting circuit 9 includes a load cell (or a linear-former) mounted under the floor of the car and outputs a voltage signal proportional to the car load. The detecting circuits 9 and 10 input their output signals mc and y into the vibration suppress circuit 17.
Another follow-up control circuit 21 calculates, based on a deviation signal Vmobs1 between the motor speed reference value Vmref1 from the speed convert circuit 14 and the presumed motor speed Vmobs, the target speed correction signal Vmobs2 of the motor that can make the presumed motor speed Vmobs follow-up the motor speed reference Vmobs. A motor speed presuming circuit 18 includes an approximate model of the motor which simulates an action of the motor 16 and presumes the rotational speed Vmobs thereof by means of an inertia moment of a model of an elevator mechanical system 22 when the model operates at the presumed speed Vmobs. Here, the model of the elevator mechanical system 22 is the approximate model of the elevator mechanical system 4.
The convenient speed control apparatus for elevator constructed as set forth above acts in the following manner. The speed convert circuit 14 inputs the car speed command value Vcref and converts it to the motor speed reference value Vmref1. The follow-up control circuit 15 inputs the deviation value Vce1 between the motor speed reference value Vmref1 from the speed convert circuit 14 and the detected motor speed Vm from the motor speed detecting circuit 5 and carries out a PI control calculation based on the deviation signal Vce1 to output the target value correction signal Vce2. The motor 16 inputs the deviation between the target value correction signal Vce2 from the follow-up control circuit 15 and the vibration compensation signal Vb from the vibration suppress circuit 17 as the motor speed reference Vmref2, and rotates so as to follow-up the speed reference Vmref2. The driving force of the motor is transmitted to the elevator mechanical system 4 so that the car of the elevator travels at a speed Vc. The car load mc and the position y of the car are detected respectively by the car load detecting circuit 9 and the car position detecting circuit 10 and inputted to the vibration suppress circuit 17.
The motor speed reference Vmref1 from the speed convert circuit 14 is also inputted to another follow-up control circuit 21. The follow-up control circuit 21 carries out the PI control calculation based on the deviation Vmobs between the motor speed reference Vmref1 and the presumed motor speed Vmobs from the motor speed presuming circuit 18 to gain the target value correction signal Vmobs and inputs it to the motor speed presuming circuit 18. The motor speed presuming circuit 18 calculates, based on the inputted target value correction signal Vmobs2, the presumed motor speed Vmobs that can suppress the vibration of the car and outputs to the mechanical system model 22 of the elevator. The elevator mechanical system model 22 calculates the inertia moment J when this model operates at the presumed speed Vmobs, and inputs the inertia moment J to the motor speed presuming circuit 18.
The vibration suppress circuit 17 inputs the deviation between the actual motor speed Vm from the motor speed detecting circuit 5 and the presumed motor speed Vmobs from the motor speed presuming circuit 18 as the vibration component Vrip and also inputs the car load detected value mc from the car load detecting circuit 9 and the car position detected value y from the car position detecting circuit 10. Further, the vibration suppress circuit 17 calculates, based on these inputs, the vibration compensation signal Vb by means of the manner set forth above. The motor 16 inputs the deviation between the motor speed target value Vce2 from the follow-up control circuit 15 and this vibration compensation signal Vb as the motor speed reference Vmref2 in order that the rotational speed of the motor follows-up the command value Vref2.
As set forth above, based on the changes of the position and load of the car, the vibration compensation signal Vb for suppressing the vibration is calculated, and thereto the motor speed correction signal Vce2 outputted from the follow-up control circuit 15 is added. The motor rotates at a speed following-up the motor speed reference Vmref2, which is the value of the added signal (Vce2-Vb), so that the vibration of the car is suppressed.
However, there have been several drawbacks as below in the speed control apparatus for elevator of the prior art. FIG. 10 shows frequency characteristic curves of the elevator mechanical system 4 corresponding to the changes of the car load. The car load is divided into three levels `heavy`, `medium` and `light`, and the three curves respectively correspond to these three levels. In FIG. 10, the horizontal axis indicates the angular velocity of the sheave (corresponding to the rotational speed of the motor 16) and the vertical axis indicates a gain of the elevator mechanical system 4 derived between the car speed command Vcref inputted from the speed convert circuit 14 and the car speed Vc outputted from the system shown in FIG. 8. As shown in FIG. 10, the car speed Vc causing the resonance in the elevator mechanical system 4 differs according to the levels of the car load.
However, in the vibration suppress circuit 17 of the prior art shown in FIG. 10, the car load detected value mc is inputted only to the gain setting circuit 20, and it is not inputted to the filter circuit 19. Namely, the filter circuit 19 refers to the changes of the characteristic caused by the changes of the car position but does not refer to the changes of the characteristic caused by the changes of the car load. Accordingly, the speed control apparatus of the prior art can not effectively suppress the vibration generated at a specific car load caused by the changes of the car load within a range of operation speed such as 20-30 rad/s! range of the angular velocity of the sheave, so passenger comfort is diminished.